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Statistical Fluctuations of Two Dimensional Turbulence

Jun, Yonggun (2006) Statistical Fluctuations of Two Dimensional Turbulence. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The statistics of two-dimensional (2D) turbulence driven by electro-magneticforce are investigated in freely-suspended soap film. The turbulentflow is analyzed using the particle imaging velocimetry (PIV) method.In this thesis, three important features of 2D turbulence are mainlystudied. First, the effects of addition of small amounts of polymers on 2Dturbulent flows are carefully investigated. As the polymer concentration$phi$ increases, large scale velocity fluctuations are suddenlysuppressed at a certain $phi$. This suppression is believed to happendue to the redistribution of saddle points of the flow. It impliesthat the saddle structures may play a role in energy-transfer to largescales. The thesis also presents 2D intermittency in inverse energy cascaderegime. In this subrange, the energy transfers from injection scale$l_{inj}$ to large scales. Intermittency is recognized and analyzedby the structure function $S_{p}(l)$ of the velocity difference betweentwo points, and log-normal model of the energy dissipation rate $varepsilon$.The analyses show signs of intermittency even though its intensityis weaker than that in three-dimensional (3D) turbulence. Finally, single-point(SP) velocity statistics are investigated, inspiredby the theory proposed by Falkovich and Lebedev (FL). This theoryreveals the connection between SP statistics and forcing statistics.For forced 2D turbulence, the SP velocity probability distribution function (PDF) deviates from Gaussian when turbulence intensity issufficiently strong, which can be explained using FL theory. In thecase of decaying turbulence, SP velocity PDF gradually evolves fromsuper-Gaussian to sub-Gaussian as time increases.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Jun, Yonggunyoj5@pitt.eduYOJ5
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWu, Xiao-Lunyoj5@pitt.eduYOJ5
Committee MemberJasnow, Daviddmj@pitt.eduDMJ
Committee MemberBerry, Guy
Committee MemberSavinov, Vladimirvps3@pitt.eduVPS3
Committee MemberGoldburg, Waltergoldburg@pitt.eduGOLDBURG
Date: 2 June 2006
Date Type: Completion
Defense Date: 30 March 2006
Approval Date: 2 June 2006
Submission Date: 21 April 2006
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: fluid; nonlinear; turbulence
Other ID:, etd-04212006-102831
Date Deposited: 10 Nov 2011 19:40
Last Modified: 15 Nov 2016 13:41


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